A self-expanding prosthesis is typically introduced into the body using a delivery device that comprises a push-pull mechanism. The delivery device comprises an outer catheter coaxially disposed and slidable over an inner catheter. The prosthesis is disposed at the distal end of the device between the inner catheter and the outer catheter. The inner and the outer catheter move coaxially with respect to each other. The prosthesis may be deployed by proximally pulling back the outer catheter relative to the inner catheter until the prosthesis is exposed.
There are numerous drawbacks to the above push-pull delivery device. For example, utilizing a conventional push-pull delivery device may cause the physician to inadvertently use excessive force and pull back the outer catheter too far, thereby prematurely deploying the prosthesis in an incorrect position within a body lumen. At this step in the procedure, repositioning of the prosthesis becomes difficult, if not impossible, because the prosthesis has already radially self-expanded into the body lumen. Additionally, retraction of the outer sheath may not be achieved with controlled movement because the physician is manually retracting the outer catheter. Manual retraction of the outer catheter may lead to inadvertent jerking of the outer catheter. Furthermore, two hands are typically needed to deploy the prosthesis with a push-pull mechanism. One hand may be required to hold the inner catheter while the other hand pulls the outer catheter and slides it back over the inner catheter. The use of two hands prevents the physician from performing another task during the procedure.
Additionally, in a typical push-pull device, the first portion of the self-expanding stent to make contact with the body vessel is the most distal portion of the stent because the sheath is pulled away from the stent in the proximal direction. This type of system may also be referred to as a “distal release” device. Distal release devices generally allow for accurate placement of the distal portion of a self-expanding stent, but often do not allow for accurate placement of the proximal portion of a stent.
Accurate placement of the proximal portion of the stent may be important in certain applications. For example, the deployment of self-expanding stents within the gastrointestinal (GI) tract is well-known. However, the use of a distal release device may prevent accurate placement of the proximal portion of the stent. As an example, foreshortening stents tend to anchor within the GI tract at the initial location that the stent makes contact with the body vessel and thereafter shorten away from that location along a central axis of the stent. Thus, when using a foreshortening stent, the distal end that initially opens is relatively easy to place with accuracy, but the final location towards the opposite proximal end of the stent is variable, oftentimes being dependent upon the extent to which the deployed stent elongates within a lumen of the target stricture. The amount of elongation may be dependent on the lumen and stricture size. Accordingly, accurate positioning of the proximal end of a foreshortening stent that is distally released may not be possible.
In some applications, there is a clinical need to achieve placement of the proximal end of the self-expanding stent that is more accurate than conventional distal release devices. For example, when there is a need to deploy a self-expanding stent at a relatively more proximal region within the esophageal region, the proximal end of the stent should ideally be deployed above the stricture but below the cricopharyngeal region of the throat to avoid aggravation of the nerves that control the coughing response. Such a need for deployment at a relatively more proximal region within the esophagaus may occur when strictures along the proximal portion of the esophagus develop following surgical esophagectomy. Additionally, malignant lesions that develop proximally in the esophagus may also be treated with self-expanding stents capable of being accurately deployed along their proximal ends.
Accordingly, in view of the drawbacks of current technology, there is a desire for a proximal release delivery system that can increase the control, accuracy and ease of placement during deployment of the prosthesis. The proximal release device may reduce the risk of malfunction, provide for ease of deployment, and allow the ability to recapture the stent after partial deployment. Although the embodiments described below may be useful for increasing the control, accuracy and ease of placement during proximal release of the prosthesis, the claimed inventions may also solve other problems.